Independence of net water flux from paracellular permeability in the intestine of Fundulus heteroclitus, a euryhaline teleost

Chris M. Wood, Martin Grosell

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

Paracellular permeability and absorptive water flux across the intestine of the euryhaline killifish were investigated using in vitro gut sac preparations from seawater-And freshwater-acclimated animals. The permeability of polyethylene glycol (PEG), a wellestablished paracellular probe, was measured using trace amounts of radiolabelled oligomers of three different molecular sizes (PEG-400, PEG-900 and PEG-4000) at various times after satiation feeding. All three PEG molecules were absorbed, with permeability declining as a linear function of increasing hydrodynamic radius. Response patterns were similar in seawater and freshwater preparations, though water absorption and PEG-900 permeability were greater in the latter. Despite up to 4-fold variations in absorptive water flux associated with feeding and fasting (highest at 1-3h, lowest at 12-24h and intermediate at 1-2?weeks post-feeding), there were no changes in PEG permeability for any size oligomer. When PEG permeability was measured in the opposite direction (i.e. serosal to mucosal) from net water flux, it was again unchanged. HgCl 2 (10 -3mmoll -1), a putative blocker of aquaporins, eliminated absorptive water flux yet increased PEG-4000 permeability by 6- to 8-fold in both freshwater and seawater preparations. Experimentally raising the serosal osmolality by addition of 300mmoll -1 mannitol increased the absorptive water flux rate 10-fold, but did not alter PEG permeability. Under these conditions, HgCl2 reduced absorptive water flux by 60% and again increased PEG permeability by 6- to 8-fold in both freshwater and seawater preparations. Clearly, there was no influence of solvent drag on PEG movement. The putative paracellular blocker 2,4,6-triaminopyrimidine (TAP, 20mmoll-1) had no effect on net water flux or PEG permeability. We conclude that PEG and water move by separate pathways; absorptive water transport probably occurs via a transcellular route in the intestine of Fundulus heteroclitus.

Original languageEnglish (US)
Pages (from-to)508-517
Number of pages10
JournalJournal of Experimental Biology
Volume215
Issue number3
DOIs
StatePublished - Feb 2012

Keywords

  • Cl uptake
  • Fasting
  • Feeding
  • Paracellular permeability
  • PEG
  • Polyethylene glycol
  • Solvent drag
  • Transcellular permeability

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Physiology
  • Insect Science
  • Aquatic Science

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